It looked like Jackie McNamara’s men would ease home when Gary Mackay-Steven put them 2-0 up.

They became slack, though, and gifted Gers a route back into the semi-final as Steven Smith pulled one back.

That made for a fraught second period before Nadir Ciftci’s late strike finally killed off Ally McCoist’s men. But Armstrong claims the guts and determination shown from the Tannadice troops blew apart the myth they can only play fancy football and never get their hands dirty.

The midfielder said: “After we went 2-0 up we were comfortable and I think that was the problem.

“You could say it was an ugly win and sometimes that is needed because you can’t play terrifically well every week.

“To win silverware you have to be at your best and we will try to do that in the final.

“But
it was said our problem earlier in the season was we couldn’t win games
when it wasn’t flowing and that we struggled to pick up results. We have answered those critics here.”

United
could, and should, have made the job easier for themselves but staying in the Cup was the bottom line on a day when they had so much to lose.

Favourites going into the clash, McNamara’s men had to deal with the pressure and Armstrong admits it was a test of character.

He
added: “We all knew Rangers had quality players and we didn’t want to belittle them before the game because we were aware of their capabilities. But we thought we could definitely win and we proved that.

“We didn’t underestimate Rangers at all. We were quite nervy, especially at 2-1, and it could have gone either way.

“But when Nadir stuck the third we had it in our minds that was it.”

McNamara’s
young guns are now just 90 minutes from glory and Armstrong is determined to cap a wonderful season with a Scottish Cup victory.

He said: “Winning a trophy would be a nice way to the end the season. But I don’t think losing out would destroy our campaign.

“There are a lot of positives and we’ve taken part in exciting games.”